This invention is directed to a dynamic image processing technique for recognizing objects of a given class which are graphically represented in a time series of successive relatively high-resolution frames of image data.
Techniques for recognizing pattern shapes of objects graphically represented in image data are known in the art. Further, techniques for discriminating between moving and stationary objects having a preselected angular orientation, or objects having any other predetermined feature of interest, are also known in the art.
In this regard, reference is now made, by way of examples, to U.S. Pat. No. 4,692,806, which issued to Anderson et al. on Sept. 8, 1987, and to U.S. Pat. No. 4,385,322, which issued to Hubach et al. on May 24, 1983.
Anderson et al. disclose an image-data reduction technique in which an originally wide field-of-view, high-reduction image comprised of a first given number of pixels is processed to derive a wide field-of-view, low resolution image comprised of second given number of pixels smaller than the first given number. Based on the location of a detected feature of interest present in the derived low resolution image, a movable window comprised of no more than the second given number of pixels can be employed to obtain the location of that narrow field-of-view portion of the original high-resolution image which contains the detected feature of interest. Anderson et al. utilize known so-called multi-resolution pyramid processor techniques to implement their image-data reduction.
While the Anderson et al. data reduction technique may operate repeatedly on a time series of successive, relatively high-resolution frames of image data, the detection of the feature of interest is similar during each operation (i.e., during each repeated operation, the feature of interest is either detected or it is not, independent of whether or not the feature of interest was detected on a previous one of the repeated operations).
Hubach et al. disclose a pattern recognition method which also employs a data reduction technique. A reference scene is first recorded and stored in a fine format and then in a coarse format. Stored coarse information of the reference scene is compared in real time with coarse information from a wide field-of-view subject scene and a correlation number (probability) indicating the percentage of match is employed to determine the location of the best match (if any) between the subject and reference scenes. Only the narrow field-of-view area of the subject scene which is in the vicinity of the coarse match is then compared with the stored fine information of the reference scene. The location of the best match is precisely determined in accordance with the highest correlation number (probability) of the match of the subject scene with the fine stored information of the reference scene. It should be noted that in Hubach et al. the stored coarse and fine reference information remains fixed.
Consider the case in which the object to be recognized is a three-dimensional movable object which is graphically represented in a time series of successive frames of image data, each of which is comprised of a two-dimensional projection of the three-dimensional object. In such a case, the size and shape of the two-dimensional projection in each of the respective frames will depend on the distance of the three-dimensional object in a direction perpendicular to the projection thereof and the angular orientation of the three-dimensional object with respect to its projection in that frame. If the three-dimensional object moves, the size and shape of its graphical representation will change from frame to frame. Thus, much less than complete information about such a three-dimensional moving-object can be obtained from any single frame. However, by cumulatively adding to the information obtained from any single frame, the information obtained from all previous frames of the times series, it becomes possible to collect sufficient information to selectively recognize the identity of such a three-dimensional movable object with great precision. The dynamic image processing method of the present invention is directed to an efficient solution to this type of recognition problem.